Maps


1   /*****************************************************************************
2    * Copyright (C) Zephyr Business Solutions Corp. All rights reserved.            *
3    * ------------------------------------------------------------------------- *
4    * The software in this package is published under the terms of the BSD      *
5    * style license a copy of which has been included with this distribution in *
6    * the LICENSE.txt file.                                                     *
7    *****************************************************************************/
8   /*
9    * Created on Nov 19, 2004
10   *
11   * Author Ben Yu
12   */
13  package jfun.parsec;
14  
15  
16  
17  /**
18   * This class provides some standard Map implementations.
19   * @author Ben Yu
20   *
21   * Nov 19, 2004
22   */
23  public final class Maps {
24    private static final Unary<Object  > _id = new Unary<Object  >(){
25      public Object   map(Object   v) {
26        return v;
27      }
28      public String   toString(){return "id";}
29    };
30    private static final Mapn<Object  []> _idn = new Mapn<Object  []>(){
31      public Object  [] map(Object  ... v){
32        return v;
33      }
34    };
35    /**
36     * Returns an identity map. map a = a.
37     * @return the Map instance.
38     */
39    public static <x> Unary<x> id(){return (Unary<x>)_id;}
40    /**
41     * Returns an identity map. map a = a.
42     * @param type the class literal for the type parameter.
43     * @return the Map instance.
44     */
45    public static <R> Unary<R> id(Class  <R> type){
46      return id();
47    }
48    /**
49     * Returns an identity map. map a = a.
50     * @return the Mapn instance.
51     */  
52    public static Mapn<Object  []> idn(){return _idn;}
53    /**
54     * Creates a map that maps any object to the same object.
55     * @param v the object that is gonna be returned from the Map.
56     * @return the Map instance.
57     */
58    public static <x, V> Map<x, V> cnst(final V v){
59      return new Map<x,V>(){
60        public V map(final x from){return v;}
61      };
62    }
63    /**
64     * Adapts a java.util.Map to jfun.util.Map.
65     * @param m the java.util.Map object.
66     * @return the jfun.util.Map instance.
67     */
68    public static <From,To> Map<From,To> jmap(final java.util.Map  <From, To> m){
69      return new Map<From,To>(){
70        public To map(final From k){
71          return m.get(k);
72        }
73      };
74    }
75    
76    /**
77     * Transform a Tok object to the wrapped token object.
78     * @return the Map instance.
79     */
80    public static <T> Map<Tok, T> toToken(){
81      return new Map<Tok, T>(){
82        public T map(final Tok o){
83          return (T)o.getToken();
84        }
85      };
86    }
87    private static final Map2 _id2 = new Map2(){
88      public Object   map(Object   o1, Object   o2){
89        return new Pair(o1, o2);
90      }
91    };
92    private static final Map3 _id3 = new Map3(){
93      public Object   map(Object   o1, Object   o2, Object   o3){
94        return new Tuple3(o1, o2, o3);
95      }
96    };
97    private static final Map4 _id4 = new Map4(){
98      public Object   map(Object   o1, Object   o2, Object   o3, Object   o4){
99        return new Tuple4(o1, o2, o3, o4);
100     }
101   };
102   private static final Map5 _id5 = new Map5(){
103     public Object   map(Object   o1, Object   o2, Object   o3, Object   o4, Object   o5){
104       return new Tuple5(o1, o2, o3, o4, o5);
105     }
106   };
107   /**
108    * Create a Map2 object that stores the two objects into a Pair object.
109    */
110   public static <A,B> Map2<A,B,Pair<A,B>> id2(){
111     return _id2;
112   }
113   /**
114    * Create a Map3 object that stores the 3 objects into a Tuple3 object.
115    */
116   public static <A,B,C> Map3<A,B,C,Tuple3<A,B,C>> id3(){
117     return _id3;
118   }
119   /**
120    * Create a Map4 object that stores the 4 objects into a Tuple4 object.
121    */
122   public static <A,B,C,D> Map4<A,B,C,D,Tuple4<A,B,C,D>> id4(){
123     return _id4;
124   }
125   /**
126    * Create a Map5 object that stores the 5 objects into a Tuple5 object.
127    */
128   public static <A,B,C,D,E> Map5<A,B,C,D,E,Tuple5<A,B,C,D,E>> id5(){
129     return _id5;
130   }
131 }
132
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